Cell Cycle and Mitosis
Cell Cycle and Mitosis
Cell Division — process by which a cell divides into 2 new
cells
2 Daughter Cells
Parent Cell
•The original cell is called the parent cell; 2 new cells are
called daughter cells
2 Daughter Cells
Parent Cell
Why do cells need to divide?
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Living things grow by
producing more cells,
NOT because each cell
increases in size
Repair of damaged
tissue
If cell gets too big, it
cannot get enough
nutrients into the cell
and wastes out of the
cell
Do you remember?
1) Which cell organelle controls all cell
functions? Nucleus
2) What does this cell organelle contain?
Genetic Information
3) What do ALL cells need in order to have the
directions/code to perform functions
correctly?
DNA
DNA
•DNA is located in the nucleus and controls all cell
activities including cell division
•Long and thread-like DNA in a non-dividing cell is called
chromatin
•Doubled, coiled, short DNA in a dividing cell is called
chromosome
Consists of 2 parts: chromatid and centromere
Compare and Illustrate DNA
DNA in NON-DIVIDING Cell
DNA in a DIVIDING Cell
•Chromatin to chromosomes illustration:
Chromatin
Duplicates
itself
Why does DNA need to change
from chromatin to chromosome?
Coils up into
chromosomes
More efficient division
o2 identical “sister”
chromatids attached at
an area in the middle
called a centromere
oWhen cells divide,
“sister” chromatids
separate and 1 goes to
each new cell
Cell Cycle and Mitosis
•Before cell division occurs , the cell replicates (copies) all
of its DNA, so each daughter cell gets complete set of
genetic information from parent cell
•Each daughter cell is exactly like the parent cell – same
kind and number of chromosomes as the original cell
•Every organism has its own specific number of chromosomes
Examples: Human = 46 chromosomes or 23 pairs
Dog = 78 chromosomes or 39 pairs
Goldfish = 94 chromosomes or 47 pairs
Lettuce = 18 chromosomes or 9 pairs
•All somatic (body) cells in an organism have the same
kind and number of chromosomes.
Examples: Human = 46 chromosomes
Human skin cell = 46 chromosomes
Human heart cell = 46 chromosomes
Human muscle cell = 46 chromosomes
Fruit fly = 8 chromosomes
Fruit fly skin cell = 8 chromosomes
Fruit fly heart cell = 8 chromosomes
Fruit fly muscle cell = 8 chromosomes
Cell Cycle -- series of events cells go through as they grow
and divide
•Cell grows, prepares for division, then divides to form 2
daughter cells – each of which then begins the cycle again
Cell Cycle Outline
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Interphase

G1: Cell Grows

S: DNA Replicates

G2: Growth &
prepares for division
•
Mitosis

Prophase

Metaphase

Anaphase

Telophase
•
Cytokinesis
Cell Cycle and Mitosis
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Interphase
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Prophase
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Metaphase
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Anaphase
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Telophase
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Cytokinesis
Get a friend and create a
sentence to help you
remember the order of the
cell cycle and mitosis. Use
the first letter of each term.
Interphase
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Interesting things happen!
1.
Cell preparing to divide
2.
Genetic material doubles
3.
Cells most of their time in Interphase
Mitosis Begins
Prophase, Metaphase, Anaphase, Telephase
•Mitosis – division of the nucleus into 2 nuclei,
each with the same number of chromosomes
•Mitosis occurs in all the somatic (body) cells
Prophase
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Chromosome pair up!
Chromosomes become
visible
Nuclear membrane
disappears
Spindle fibers form
Prophase
Metaphase
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Chromosomes meet
in the middle!
Spindle Fibers
connect to
chromosomes
Metaphase
Anaphase
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Chromosomes get
pulled apart
Spindle fibers pull
chromosomes to
opposite sides
Anaphase
Telophase
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Now there are two!
Chromosomes
uncoil
Spindle fibers
disappear
Two nuclei are
formed
Telophase
Cytokinesis
Cytokinesis — the division of the rest of the cell
(cytoplasm and organelles) after the nucleus
divides
In animal cells the cytoplasm
pinches in
In plant cells a cell plate forms
•After mitosis and cytokinesis, the cell returns to
Interphase to continue to grow and perform
regular cell activities
Mitosis is a type of asexual
reproduction.
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There are two types of reproduction:
Asexual Reproduction
• parent
reproduces by itself
• offspring is genetically
identical to “mamma”
Sexual Reproduction
•Offspring is genetically
unique
• creates diversity within
population
Asexual Reproduction
1)
2)
3)
4)
5)
6)
Mitosis
Binary Fission
Budding
Spores
Regeneration
Vegetative
Propagation
1) Mitosis
produce 2 identical daughter cells with
the same # of chromosomes as the
parent cell. (identical)
2) Binary Fission
• a parent cell splits
into 2 daughter
cells of = size
• w/ prokaryotes
3) Budding
• a new, duplicate
organism forms at the
side of the parent and
enlarges until an
individual is created.
4) Spores
• spores are surrounded by
a tough coat to help
them survive harsh
conditions. .. Produced
and released
5) Regeneration
6) Vegetative
Propagation
stolons
• growth of new
tissues/organs to replace
those injured or lost.
• Common in invertebrates,
especially Asteroidea (Sea
Stars) and Annelida
(Worms).
* In some multicellular plants
* new plants develop from the
roots, stems, or leaves of the
parent.
Sexual Reproduction
1) Meiosis
Cell division that results in haploid
gametes; used for sexual reproduction
Haploid?
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When a gamete (sperm
or egg) of an organism
has HALF of the full
amount of
chromosomes
Hap
Half
Remember, human
cells have 46
chromosomes? Then
the haploid # is 23
Sperm
Egg
Meiosis
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Occurs in the same four phases as mitosis but in
two steps: Meiosis I and Meiosis II
Meiosis I
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All chromosomes make
copes of themselves
This doubles the # of
chromosomes in the cell
Meiosis II
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Begins in same two cells
created by Meiosis I
Creates FOUR new haploid
cells
Occurs in a manner very
similar to mitosis
Outline of Meiosis
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Meiosis I
–
Prophase I
–
Metaphase I
–
Anaphase I
–
Telophase I
Meiosis II
–
Prophase II
–
Metaphase II
–
Anaphase II
–
Telophase II
Prophase I
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Homologous
chromosomes from
each parent pair up!
They form two
attached sets of
chromatids called a
tetrad
There are MANY ways
the chromatids can
line up: this is one
source of genetic
variation.
Homologous
chromosomes:
•1 from each parent
•carry
genes that
control the
same
inherited
traits.
Metaphase I
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Each tetrad meets
in the middle!
Spindle fibers
connect
centromeres
Crossing over of
chromosomes may
occur to provide
additional genetic
variation – 2nd
source of genetic
variation
Anaphase I
●
•
Tetrads get pulled
apart
Homologous
chromosomes
move to opposite
ends
Telophase I
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Cells may finish
cytokinesis OR
proceed
immediately with
Meiosis II
Prophase II
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Chromosomes did NOT
replicate
At this point, the cell
is haploid because it
no longer has one of
every kind of
chromosome that was
in the original cell
Metaphase II
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Sister chromatids
line up on individual
spindle fibers
Anaphase II
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Sister chromatids
are separated into
each new cell
Each new cell now
has only HALF as
many chromosomes
as the parent cell
in Prophase I
Telophase II
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Each of the four
new cells completes
reforming nuclei
and cytokinesis
separates the four
new hapliod cells
How does meiosis lead to genetic
variation?
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Look back at Prophase I & Metaphase I, what
may lead to genetic variation?
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There are MANY ways the chromatids can line up
–
Crossing over of chromosomes may occur
What is another factor that could lead to
genetic variation?
–
Random combinations of sperm and eggs
Interphase
Interphase
Meiosis 1
Metaphase 1
Anaphase 1
Telophase 1
Review!
Prophase 1
Meiosis 2
Prophase 2
Metaphase 2
Cytokinesis
Anaphase 2
Cytokinesis
Note..
Male gametes
4 haploid gametes …
4 sperm by way of
spermatogenesis
Female gametes
4 haploid gametes …
1 Ovum (egg) & 3 Polar
Bodies by way of oogenesis
Sometimes cell division doesn’t go as
planned…
Cell Division Regulation
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Internal and external
factors regulate cell
division.
Cancer is the uncontrolled
growth and division of
cells.
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Cancer cells can kill an
organism by crowding out
normal cells, resulting in the
loss of tissue function.
Cancer
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Benign – cancer cells
typically remain
clustered together
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Malignant – cancer
cells can break away or
metastasize
cancer cell
normal cell
bloodstream
metastasize
Benign
Malignant
Causes of Cancer
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Internal Factors
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Inheritance
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Mutations
External Factors
–
Carcinogens are substances
that are known to produce
and promote the
development of cancer.
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Radiation
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Chemical
–
Viruses
Skin
Cancer
Nondisjunction Mutations
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Improper separation of sister chromatids may
result in a cell having one too many
chromosomes (trisomy) or not having one of
a certain chromosome (monosomy)
Karyotype – a picture of an
individual’s chromosomes
so that the types of
mutations might be seen
Trisomy 21 – Down Syndrome
Trisomy 18 - Edward's Syndrome
Meiosis Square Dance